Large screen projection display device employing a printing cathode ray tube



July 26, 1966 A. H. ROSENTHAL 3,263,929

LARGE SCREEN PROJECTION DISPLAY DEVICE EMPLOYING A PRINTING CATHODE RAY TUBE Filed March 28, 1963 INVENTOR. ADOLPH H.ROSENTHAL,DECEASED. W BY LILLY S. ROSENTHAL, EXECUTRIX A 1Q BY United States Patent LARGE SCREEN PROJECTION DISPLAY DEVICE EMPLOYING A PRINTING CATHODE RAY TUliE Adolph H. Rosenthal, deceased, late of Forest Hills, N.Y., by Lilly S. Rosenthal, executrix, Forest Hills, N.Y., assignor to Kollsman Instrument Corporation,

Elmhurst, N.Y., a corporation of New York Filed Mar. 28, 1963, Ser. No. 268,332

4 Claims. (Cl. 178-7.88)

The instant invention relates to display devices in general and more particularly to a means for obtaining a large screen display derived from electrical signals.

Prior art devices for obtaining large viewable images from electrical signals have, for the most part, been limited to the control of a mechanical stylus by servo motors. The stylus inscribed lines on a metallized glass plate by scratching away a metal coating. At the same time the image is being inscribed on the plate or slide the image is projected on a large screen by a lantern slide projector.

This system has proven expensive to produce and has also performed less than satisfactorily. In particular, the time response of the mechanical stylus is very slow and the time for erasing a previous image is too great.

The instant invention provides a device for large screen display which utilizes a so-called printing cathode ray tube. The controlled impingement of the electron beam upon the face or target area of the tube places local charges on appropriate points of the target area. These charges are effective to deflect local areas of a membrane positioned adjacent to the face of the tube in close proximity thereto. A light beam is arranged to be reflected from mirrored portions of a diaphragm on to a reflecting surface of the membrane.

The membrane, diaphragm and light source are so arranged that light reflected from undeflected portions of the membrane will impinge upon the mirrored portions of the diaphragm while light reflected from deflected portions of the membrane will be directed to transparent portions of the diaphragm, further passing through an enlarging lens and is directed upon a viewing screen. Thus, the only light reaching the viewing screen will be light reflected from deflected portions of the membrane.

Erasing of the image is a simple matter in that it is only necessary to remove the local charges from the target area so that the membrane is no longer deflected. Removal of the charges at the target area takes place by simply switching the potential of the cathode ray tube anode.

Accordingly, a primary object of the instant invention is to provide a novel arrangement for a large screen display of images generated by electrical signals.

Another object is to provide a novel device of this type which utilizes a printing cathode ray tube.

Still another object is to provide a novel device of this type in which there is a deflectable membrane with a light reflecting surface thereon.

A further object is to provide a device of this type having a novel light diaphragm construction.

A still further object is to provide a novel device of this type in which the image is formed by charged particles on a membrane positioned adjacent to the face of a printing cathode ray tube.

These as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a schematic of -a display system constructed in accordance with the teachings of the instant invention FIGURE 2 is an elevation of a light reflecting and transmitting diaphragm looking in the direction of arrows 2-2 of FIGURE 1.

FIGURE 3 is a fragmentary cross-section taken through the target area of a printing cathode ray tube.

FIGURE 4A is a graph plotting secondary emission against anode potential for a typical printing cathode ray tube.

FIGURE 43 is a diagram illustrating typical local voltage charges along a vertical line of the cathode ray tube target area.

FIGURE 5 is a schematic illustrating another embodiment of this invention in which the image is obtained by depositing charged particles.

Now referring to the figures and more particularly to FIGURES 1 through 4B. The display device of FIG- URE 1 comprises printing cathode ray tube 10 which is of a type described in United States Patent 2,777,745 and includes a screen or target area 11. Target area 11 is constructed of insulating material, preferably glass 12, having a plurality of wires 13 embedded therein and extending therethrough. Wires 13 are arranged as a mosaic with spacings of approximately 40 wires per millimeter. Intensifier anode 14 is positioned adjacent to the rear of target area 11 and in close proximity thereto. High voltage source 15 and voltage divider 16 provides suitable accelerating and focusing volt-ages in a manner well-known to the art. The presence or absence of the electron beam as well as its position at the target area is controlled by the source 17 of control signals which operate in a manner well-known to the art.

Anode 14 is connected through switch arm 18 to either switch terminal 19 or switch terminal 20. Terminal 20 is at a more negative potential with respect to the ground than is terminal 19.

The outside surface of target area 11 is confronted by a thin membrane 25 of metal foil or plastic such as Mylar with the surface of membrane 25 remote from target area Ill having a metallic mirrored surf-ace so as to represent a plane mirror. Membrane 25 is spaced from target area 11 but this spacing is very small, being in the order of a small fraction of a millimeter. In any event, the spacing is close enough so that local charges deposited on wires 13 by the electron beam will distort the electric field between membrane 25, which is at ground potential, and the target area so that membrane 25 will assume a dimple at locations where the electric field is distorted.

Light emanating from source 26 passes through lens 27 to illuminate rectangular aperture 28. Light passing through aperture 28 is imaged by condenser lens assembly 29 on diaphragm 30.

Diaphragm 30 is a planar member oriented at a 45 angle with respect to optical axis XX. As clearly seen in FIGURE 2, diaphragm 30 consists of transparent member 31 carrying a number of parallel reflecting strips 32 separated by interspaces equal in Width to the width of strips 32.

Light reaching the reflecting strips 32 from lens assembly 29 is directed towards lens 33 positioned along optical axis XX in front of diaphragm 25. The distance between lens 33 and diaphragm 30 is equal to the focal length of lens 33. Thus, light directed by reflecting strips 32 through lens 33 is collimated, with the parallel rays impinging upon membrane 25. These rays are reflectcd back through lens 33 to diaphragm 30.

If there are no local charges at target area 11 membrane 25 is in an undisturbed condition so that all light impinging thereon will return to reflecting strips 32 and in turn be deflected at right angles to optical axis XX. However, if local charges are present at target area 11 local areas of membrane 25 will be distorted. These distorted areas will reflect light toward the transparent portions of diaphragm 30 and this light will pass through 3 diaphragm 30 to screen 37. Light rays passing through diaphragm 30 are diverged by lens 36 positioned to the rear of diaphragm 30 thereby producing an enlarged image on screen 37. This image is a visual presentation of the distorted portions of membrane 25 resulting from local charges on screen 11.

Membrane 25 is at a positive potential with respect to anode 14. If this potential difference is low so that the secondary emission factor 6 (FIGURE 4A) is smaller than 1, the portions of screen 11 which are bombarded by the electron beam will move toward the potential of cathode 41 and a strong local field will exist between membrane 25 and the charged portions of screen 11. This is indicated in FIGURE 4A in which secondary emission 5 is plotted against the voltage V present at anode 14 with the secondary emission factor 6 between larger than 1 between points A and A.

To erase the charged image on screen 11, the potential on anode 14 is increased to a point where the secondary emission factor 6 is greater than 1. This is accomplished by moving switch arm 18 from contact 19 to contact 20. By this operation of switch arm 18 the local screen potential moves toward the sticking potential A, and from this point local potential values can be lowered as indicated in FIGURE 4B.

There is a relationship between charge sensitivity and deflection of membrane 25. Further, an increase in tension on membrane 25 increases the definition and decreases the sensitivity, i.e. deflection for a given charge. Thus, it is desirable to provide adjustable supporting ring 42 for mounting membrane 25 so that the tension thereof may be adjusted.

It is significnat to note that the metal surface of membrane 25 acts both as an optical mirror and as an electrical conductor.

It is noted, that instead of utilizing membrane 25 as the image forming medium, one can make use of a viscous liquid film. In such an arrangement the screen of the cathode ray tube would be in a horizontal position and the liquid film would be supported by an insulating material spaced over the front of the screen. The liquid film would be mechanically, and thereby optically, distorted by the charges on the tube screen.

In another embodiment the deflectable membrane would consist of a thermoplastic material which would be heated during writing, as by a dielectric heater, and upon cooling of the membrane the image would be frozen in place for any desired period of time.

FIGURE 5 illustrates another embodiment of this invention in which the membrane 25 of FIGURE 1 is replaced by an insulating film 51 stretching across the face of printing cathode ray tube 50 in intimate contact therewith. It is to be understood that the control signals and electrode potentials are supplied to the elements of tube 50 in substantially the same manner as these voltages are applied to tube 10.

The charges deposited on the tube face by the electron beam extend through insulating film 51 and are of sufiicient magnitude to attract particles to which film 51 is exposed.

The exposure of film 51 to the particles is accomplished by means of magnetic brush 52 mounted to rod 53 which is periodically moved down into powder chamber 54. The powder 55 in chamber 54 is mixed with magnetic particles which charge powder 55 tribo-electrically. As brush 52 moves upwardly out of chamber 54 it carries particles 55 rubbing these particles across film 51. The particles 55 stick to screen 51 at locations where charges exist.

Typically, film 51 is black and powder 55 is white or of some other contrasting color. Light source 56 illuminates film 51, with the image formed thereon by powder 55 being enlarged by objective lens 57 and then projected upon screen 58.

Thus, this invention provides a novel construction for a large screen display device utilizing a cathode ray tube as the initial image-forming means. This results in rapid image formation with the images being readily erasable after being restrained for any desired period of time.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows;

1. A device of the class described comprising a printing cathode ray tube having a target area, means for generating an electron beam and directing said beam to said target area, and means for deflecting said beam to selected points of said target area thereby establishing local charges at said points; a sheet external of said tube adjacent to said target area; first means impinging upon said sheet to produce at said sheet an image relate to points of said target area reached by said electron beam; a screen; and second means for enlarging and projecting said image onto said screen for viewing; said sheet comprising a membrane closely spaced from said target area; said membrane being deflectable at local areas thereof; said membrane including a light reflecting surface on the side thereof remote from said target area; a light source for generating a light beam constituting said first means; a diaphragm including a reflecting portion and a transparent portion; said reflecting portion positioned to reflect said light beam to said light reflecting surface; said image being formed by deflection of said membrane at points thereof opposite points of said target area traversed by said electron beam; said transparent portion of said diaphrgam positioned to pass portions of said light reflected from deflected parts of said light reflecting surface to said screen.

2. The device of claim 1 in which the second means includes a lens whose optical axis is substantially perpendicular to said target area; said lens being positioned between said diaphragm and said screen; said diaphragm including a planar member disposed at a first angle with respect to said optical axis; said light source being positioned so that the light beam emanating directly therefrom is at an angle to said diaphragm equal to said first angle and crosses said axis where said diaphragm is located.

3. The device of claim 1 in which there is collimating lens interposed between said diaphragm and said light reflecting surface; said collimating lens being spaced from said diaphragm by a distance equal to the focal length of said lens.

4. The device of claim 1 in which the cathode ray tube also has an anode positioned in close proximity to said target area; a potential source connected to said diaphragm; and switch means for selectively connecting said anode to a first and a second potential of said source with the first potential being such that charges may be deposited at said target area and the second potential being such that charges at said target area are neutralized; said first and said second potentials being negative with respect to the potential at said diaphragm.

References Cited by the Examiner UNITED STATES PATENTS 2,996,573 8/1961 Barnes 34674 3,041,395 6/1962 Mast 1787.88 3,102,162 8/1963 McNaney 1786.6 3,128,336 4/1964 Semple 1786.6

DAVID G. REDINBAUGH, Primary Examiner.

R. L. RICHARDSON, Assistant Examiner. 

1. A DEVICE OF THE CLASS DESCRIBED COMPRISING A PRINTING CATHODE RAY TUBE HAVING A TARGET AREA, MEANS FOR GENERATING AN ELECTRON BEAM AND DIRECTING SAID BEAM TO SAID TARGET AREA, AND MEANS FOR DEFLECTING SAID BEAM TO SELECTED POINTS OF SAID TARGET AREA THEREBY ESTABLISHING LOCAL CHARGES AT SAID POINTS; A SHEET EXTERNAL OF SAID TUBE ADJACENT TO SAID TARGET AREA; FIRST MEANS IMPINGING UPON SAID SHEET TO PRODUCE AT SAID SHEET AN IMAGE RELATE TO POINTS OF TARGET AREA REACHED BY SAID ELECTRON BEAM; A SCREEN; AND SECOND MEANS FOR ENLARGING AND PROJECTING SAID IMAGE ONTO SAID SCREEN FOR VIEWING; SAID SHEET COMPRISING A MEMBRANE CLOSELY SPACED FROM SAID TARGET AREA; SAID MEMBRANE BEING DEFLECTABLE AT LOCAL AREAS THEREOF; SAID MEMBRANE INCLUDING A LIGHT REFLECTING SURFACE ON THE SIDE THEREOF REMOTE FROM SAID TARGET AREA; A LIGHT SOURCE FOR GENERATING A LIGHT BEAM CONSTITUTING SAID FIRST MEANS; A DIAPHRAGM INCLUDING A REFLECTING PORTION AND A TRANSPARENT PORTION; SAID REFLECTING PORTION POSITIONED TO REFLECT SAID LIGHT BEAM TO SAID LIGHT REFLECTING SURFACE; SAID IMAGE BEING FORMED BY DEFLECTION OF SAID MEMBRANE AT POINTS THEREOF OPPOSITE POINTS OF SAID TARGET AREA TRAVERSED BY SAID ELECTRON BEAM; SAID TRANSPARENT PORTION OF SAID DIAPHRAGM POSITIONED TO PASS PORTIONS OF SAID LIGHT REFLECTED FROM DEFLECTED PARTS OF SAID LIGHT REFLECTING SURFACE TO SAID SCREEN. 